It is known to conduct tests to identify hearing impairments in humans (also known as "hearing screening"). It is critical and advantageous to determine whether or not any hearing impairments exist at an early age, such as in newborns and infants. This is because the earlier a problem is diagnosed and therapy undertaken, the more likely the therapy or other intervention will minimize the potential problems and costs associated with the identified hearing impairments or loss.
Over the years, hearing screening techniques have been developed which inject a sound input into the ear and detect a response to that input. The response is related to the characteristics of the sound input and the conditions inside the ear, the neural connections, and the vibration transmission mechanism of the ear. The response can be analyzed to assess the hearing of the patient.
In many cases, and in particular in the case of infants, hearing screening is performed by using an ear phone having a cavity that fits closely about the ear. Auditory tones or "clicks" are fed into the ear phone cavity, and the response generated by the patient's ear and the neural conduction system in response to the auditory tones is sensed by a transducer. The transducer may be, for example, a microphone, suitable electrodes, piezo electric materials and like devices that generate signals representative of the response to the auditory input. These signals are then processed and the result (as well as the detected signals, if desired) can be displayed on a monitor or other viewing device for analysis of the patient's hearing.
A common problem using this method is that ambient noises, internal or external to the cavity, are capable of interfering with the stimulus or the response signals, and, thus, the result. In most cases, the monitoring equipment has mechanisms, such as microphones, for detecting and compensating for ambient background noise. However, compensating for noise inside the cavity is difficult.
U.S. Pat. No. 4,930,520 to Liverani provides a disposable ear phone for testing the hearing in infants which includes a toroidal baffle of anechoic, insulative foam, a clear planar window plastic sheet adhered to one side of the baffle defining a cavity, and an adhesive coating on the other side of the baffle for bonding the disposable ear phone to the region surrounding the infant's ear. The ear phone is capable of being used with transducers for transferring acoustical energy through a pneumatic tube to the infant's ear for testing. The Liverani device has been commercialized and is sold under the trademark EAR COUPLERS.RTM. disposable earphones by Natus Medical Incorporated, the assignee of this invention.
One of the problems with the Liverani device is that the ear phone is somewhat cost-ineffective in that the entire ear phone is not re-usable and must be disposed of after each use, and one device is used per ear. In particular, the construction and use of the device requires, according to accepted general medical practices, that after use it be disposed of as medical waste. Another problem of the Liverani ear phone is that its construction is not capable of adjustment for infants with different size ears. As a result, it is necessary to manufacture different size ear phones and maintain an inventory of the different sizes to obtain acceptable test performance for patients having different sized ears.
Thus, there remains a need for an improved ear phone that overcomes the problems of the known device and, further, provides advances that improves the attenuation of ambient and external noise inside the cavity of the ear phone.